Currently there is no standard mechanism for creating, distributing and deploying applications on containers. Applications that need orchestration for multiple containers and hosts require hand-crafted customization that is difficult to replicate and manage, not to mention time-consuming. Nulecule is a specification for defining the packaged contents, including metadata, dependencies and orchestration providers, of container-based applications. Atomic App is the reference implementation of Nulecule that provides an easy method for packaging, distributing and running applications.